Since I've been out assessing lawns for the 2011 season, one problem seems to be reoccurring this year; vole damage. I've seen it on new and established lawns alike--- one more middle finger from Mother Nature after last year when every problem known to lawn surfaced.
First of all if you don't know what a vole is, take a look at the little mouse-like critter on the top left. This my friends is the vermin that has created a highway of scribbled throughout your lawn. The one that is now visible with the spring thaw and could destroy your garden and trees if they are not dealt with. I say they because they are baby making machines and where there is one vole there are surely now others.
The last resort I would suggest would be using an anticoagulant bait like Warfarin besides voles quickly become bait shy when they realize you're trying to poison them. Plus you run the chance of affecting others, birds,cats, dogs....children and you don't want that.
I would also advise against putting down traps unless they capture humanely and you can catch and release.
Instead there are a few natural ways to deal with the scourge. People with outdoor cats do not seem to have this problem and why would they, the average cat catches three to four voles a day....but if you are short on Felines...
I have also heard that laying a stick of Juicy Fruit at the base of their runway can help dramatically. The little buggers apparently love the stuff and they can't digest the gum so, problem solved.
Repairing the damage: If it isn't extensive the lawn should repair itself once the season starts. Rake up the thatch lightly with a rake, (if it hurts your back, you're doing it too hard), and over-seed if you feel the area will not fill in quickly.
On larger damaged areas where the root system has been destroyed, clear away the debris---again lightly---with a rake and reseed the damaged area. All this is a pain in the ass--- I know, but a necessary evil if you want to keep the weeds from moving in and taking advantage of bare spots.
You've already given up the vole position, you don't want to find yourself the long-shot to having a winning lawn.